Process of clarifying sugar solutions



July' 2 i94- H. B. GusTAFsoN ET AL 2,402,950

. PROCESS 0F CLARIFYING SUGAR SOLUTIONS 2 Sheets-Sheet l Filed July 22,1942 mmm B INVENTO BY 4UJl/z l July 2, 194s.

H. B. GUsTAFsoN ETAL 2,402,960 PROCESS OF CJLRIFYING` SUGAR SOLUTIONSFiled July 22, Y1942 2 Sheets-Sheet 2 Y JZ f5 d jf Patented July 2, i946UNiTED. STATE s `PATENT oFFicE PROCESS F CLARIFYING SUGAR SOLUTIONSinning B. Gustafson, Hinsdale, and Lewis A.

Paley, Glen Ellyn, Ill., assig'nors'to Inflco Incorporatcd,Chicago,.lll., a corporation of Dela- Ware Application July 22, 1942,Serial No. 451,950

the use of roller presses, and that derived from the sugar beet by thediffusion battery, is subject to inversion or hydrolysis if subjected toelevated temperatures while in an acid condition. Cane sugar juice fromthe roller mill has some acidity and the beet sugar juice from thediffusion battery has somewhat less acidity. The cane juice contains asubstantial amount of invert sugar while the beet juice has little ornone. Sugar mill operators guard carefully against causing inversion intheir sugar juice and the time honored method of doing this isto raisethe pH of 3 Claims. (Cl. 127-46) the juice by the addition of lime to 8or 9 or even higher. After this, the practice is to heat the juice ashigh as to the boiling point to precipitate colloidal matter whichoccurs in large amounts in the raw juice.

The use of zeolite for the purification of sugar juices has been triedto a ylimited degree and certain difficulties have arisen due to thelarge amount of colloidal material present in the raw' juice. In waterpurification, the zeolites are used in column beds and the water ispassed through the beds so that exchange can take place between ionspresent in the water and the ions in the base exchange material.However, -in sugar puriflcation the column treatment of the sugar juiceis impractical because of the high percentage of colloids present in thejuice whichy` quickly plug up the pores of the zeolite bed and renderfurther passage of the juice through the lbed impossible. To overcomethis difiiculty, it has been necessary to give the-juice preliminary-defecation or purification treatment consisting of raising the pI-I ofthe juice or alkalinity through the use of lime, heating the juice,carbonating with carbon dioxide, ltering, followed by a second stage ofliming andcarbonation and filtering all in 'an eort to get rid. of thecolloids which plug up the zeolite bed.` Furthermore between vthehydrogen exchange bed and the acid removal bed of zeolite, it has beenfound necessary to use a bed of acti- We have found that by lowering thepH of the raw juice when first produced, instead of raising its pH andincreasing its alkalinity, as is customary, a great volume of dissolvedor suspended colloids is immediately precipitated. This precipitationreaction can be considerably improved by mixing with the raw juice ahydrogen carbonaceous zeolite in a suitable type of apparatus which willbe subsequently described. The hydrogen carbonaceous zeolite has theability toI remove metal ions such as potassium, calcium, sodium andmagnesium ions from the sugar juice and form acids in the juice whichlower the pH of the juice and precipitate colloidal matters along withorganic acids which are combined with the base metals. f

We have found, however, lthat the precipitate produced in this step ofthe process is very slimy and exceedingly dilcult tolter unless suitablesteps are taken to secure its concentration and occulation. After thejuice is properly purified by the addition of hydrogen carbonaceouszeolite and the suitable concentration and removal of the precipitate,the puried juice is passed through an exchange bed of material capableof removing excess acids from the juice. The entire process takes placein a very 'short time and the juice is maintained in a cold state duringthe vated carbon to take out additional colloidalv I n rated to apalatable syrup without further purifiapparatus required.

entire process so that no danger of inversion occurs. The hydrogencarbonaceous zeolite which we contemplate using is preferably a low costproduct which may be discarded along with the precipitate produced, andmay 'not be subsequently regenerated through the use of acid as iscustomary with zeolites in granular form supported in filter beds.

An object of this invention therefore is to provide a process fortreating 'sugar juices which will be simple to operate and which willinvolve a low cost of treating chemicals.

, Another object of the inventionl is to provide a process of treatingsugar juices in which the pH of the juice is immediately lowered toprecipitate colloidal matter and the juice is kept cold during theentire process to prevent inversion of the sugar.

A further object ofthe invention is'to produce a high purity sugar juice-which may be evapocation; also to improve processes forthe purincationof sugar juice mother respects hereinafte specified and claimed. v

Reference is 'to be had to the accompanying drawings forming a part ofthis application in 6 5 which y f Fig. 2 is a longitudinal centralsectional eleva-A tion through an apparatus suitable for carrying outour improved process,

Fig. -3 is a transverse sectional view through the apparatus, and

Fig. 4 is a plan view of the apparatus. As seen in Fig. 1, the raw juiceis sent directly to the precipitation apparatus which will be more fullydescribed, and hydrogen zeolite preferably but not necessarily of thecarbonaceous type is fed continuously to the precipitation apparatus. Asa result of the reactions described, a voluminous precipitate is formed.This may be removed from the juice in any desired manner together withthe zeolite material as described later. The colloidal material isremoved from the precipitation apparatus in the form of a stiff mudwhich requires no ltration because of the special concentratingapparatus which is used. 'I'his mud may be treated for the recovery ofbyproducts of value such as glutamic acid and aconitic acid in' the caseof cane juice. Potassium sulphate is another byproduct which may berecovered and used for fertilizer.

'I'he claried sugar juice from the precipitation apparatus may behandled in different ways according to the nal product desired, but inour preferred process it passes directly through a bed of a granularmaterial capable of removing acid from the sugar Juice. The granularmaterial used in the acid exchange bed is preferably a synthetic resinsuitable for producing the desired results, and a number of these resinsare sold in commerce. The column of acid removal material eventuallyloses its capacity of removing acid from the sugar juice and must beregenerated by the use of a dilute alkali. The sugar in the bed is'rstWashed out with water in order to prevent vloss of sugar before passingregenerating alkali solution through the bed. The sugar juice afterpassing through the acid removal material, or anion exchange material asit is sometimes called, is now neutral and free of colloids and ash andis ready to be passed directly to the evaporators and is evaporated to asyrup. This syrup is very light in color and pleasing to the taste scthat it may be solddirectly as liquid sugar to milk processing plants,bottling works, cereal manufacturers, etc. However, if it is desired toproduce a. granulated sugar, the purified syrup is further evaporated inth'e vacuum pan and then sent to the crystallizer. The granulated sugarfrom the crystallizer is passed through a dryer and is then bagged upfor shipment in the usual channels oi commerce.

A The apparatus for treating the raw sugar juice with' hydrogen.carbonaceous zeolite shown in Figs. 2, 3 and 4, consists in a tank i0`which is -preferably but not necessarily rectangular in form andincludes a bottom II and a cover I2. The tank I is divided into twocompartments A and B by a partition I2. Draft tubes I3 and I4 arepositioned within the compartments A and B respectively. Each of thedraft tubes I3 and I4 is formed with a restricted upper cylinder Y I5and I6 respectively and an outer draft tube I1 and I8 extends aroundeach of the cylinders I5 and I6 respectively so as to form spaces I9 andtherebetween. Sloping or frusto-conical sections 2l and 22 connectthe-draft tubes I 3 and I4 with the cylinders I5 and IG. respectively.

The bottom of draft tubes I1 and I3 extend somewhat above thefrusto-coni'cal sections 2| and tions 40 and 4I.

gear not sh'own. Sugar juice to be treated is introduced into theprecipitation chamber A through a pipev 30 which passes through the Wallof draft tube I3. Hydrogen carbonaceous zeolite is also introduced intothe precipitation chamber A through pipe 32 which' passes through thewall of the draft tube I3 somewhat above the pipe 30 so that the sugarjuice and the preferably powdered precipitating zeolite are introducedat spaced points cipitation chamber A to insure a mixing of the juicewith' precipitate before mixing with the zeolite. Purified juiceoverowing into launder 23 passes through a pipe 34 to the secondprecipitation chamber B Where the pipe extends into the draft tube I4. Apipe 35 extends into the draft tube I4 of the precipitation chamber Bsomewhat above the pipe 34 and serves for introducing an additional doseof hydrogen carbonaceous zeolite in a second stage treatment of thejuice, thereby further lowering the pH of the juice and precipitatingfurther colloids and impurities. l A

The action of the carbonaceous zeolite on the sugar juice is threefold:(1) the metals of the salts in solution in the sugar juice are taken upby the zeolite and replaced by hydrogen from the zeolite, (2) theacidity in the sugar juice is increased and the pH is lowered so as toprecipitate colloids from the bodies in the sugar juice are adsorbed bythe carbon in the carbonaceous zeolite. The principal metal in the sugarjuice is potassium and part of the potassium is combined with organicacids. The liberation of the organic acids causes them in general toprecipitate.

The result of all of these actions on the sugar juice by thecarbonaceous zeolite is to produce a slimy precipitate or sludge whichis rather difficult to filter and is of low concentration, that is, theamount of dry solids in the sludge is rather low. In order toconcentrate this precipitate, longitudinal upright partitions 38 and 39are formed in the precipitation chambers A and B, the partitions 38 and39 terminating at their lower end in inclined partitions 40 and 4I.Inclined filler plates 42 and 43 are attached to the parti- 'I'he actionof the propellers 28 is to cause a constant circulation of theprecipitate and the sugar juice under treatment so that precipitationtakes place directly in contact with previously formed particles ofprecipitate thus tending to produce larger flocs or more concen tratedprecipitate. When the precipitate or slurry level builds upslightlyabove the top of concentrator partitions 38 and 39, a certain percentageof the precipitate overflows into concen trator chambers C and D. Aconveyor screw 46 and 41 is rotatably mounted in the bottom of eachconcentrator chamber C and D respectively. It will be noted that thescrew conveyors 46 and 4l are in two sections, one left-hand and onerightfhand. A sprocket wheel 5I is mounted on the shaft 50 to drive thescrew'conveyors.I vChain 52 connects the sprocket 5I to a sprocketlisugar juice, and (3) colored,

mounted on a shaft 54. A worm wheel 55 is secured to one end of shaft 54and meshes with a worm 56 which is mounted on a worm Ishaft 51. A belt58 connects a pulley 59 to a pulley 6U on the shaft of a motor 6|. Theaction of the driving mechanism described is to slowly convey theprecipitatein the bottom of concentrator chambers C and D to the endwalls 62 Land 63 of precipitation chambers A and B. The body of eachscrew conveyor 116 and 41 is of relatively long pitch while the ends osaid screw conveyor have a relatively short pit h and are ralso taperedtowards the end to fit within a frusto-conical sleeve 613, whichterminates in an outer valve seat 65. A threaded valve stem 66 having anoperating handle 61 engages a threaded opening in a bracket 58, th'evalve stem B6 having a conical valve 59 registering with the valve seat65.

In order to insure that all the slimy precipitate is delivereddownwardly to the screw conveyors i6 and t1, especially along theinclined partitions l0 and 4 I, we provide rotatably mounted scrapershafts 12 and 13 which pass through the precipitation chambers A and'Babove each of the concentrator chambers C and D. A plurality ofsprockets .1li are secured to the scraper shafts 12 and 13 and scraperchains 16 are suspended from the sprockets l. Scraper" bars 'l1 connecteach pair of chains 16 and 4are arranged to slide along the inside ofvpartitions 38, 39, 40 and 'll as the shafts 12 and 13 rotate. A chain80 connects a sprocket wheel 8| on each of the shafts 12 and 13 to asprocket'wheel 82 on 4shaft 54 so that the Scrapers will always rotatewhen the concentrating screws are rotating. The action of the taperedsection on the-screw conveyors 45 and 41 is to concentrate theprecipitate still further by squeezing the sugar juice out of theprecipitate, the juice remaining in the precipitation tanks A and B. Thestiffness or consistencyof the mud delivered by the screws QB and t1 isregulated by the position of the valve 69, relative to its valve seat65, thus regulating the back pressure on the [mud discharge. alpparatus.Fibrous material, such as comminuted bagasse or beet pulp may beintroduced if desired into each .concentrator chamber C and D by a starfeeder 86 and pipe 81 -so as to give more body to the precipitate andsecure a better squeezing action of the screws in sleeves 66. As analternate sludge concentration means, we may use a suitable centrifuge,not shown, of the type used for separating liquids from solids. Drain 85is provided in the bottom of each precipitation chamber or cell A and B.Purified juice from cell B passes from launder 24 through a pipe 88 to apoint of use orto a third cell. While the invention may be carried outin a single compartment precipitation chamber, greater fiexibility andhigher purity of juice is obtained -by using a double or trebleprecipitation chamber. Thus a limited amount of hydrogen zeolite isadmitted linto precipitation chamber A so as to lower the pH of thesugar juice to about 3.0 to 4.0. This amount of acidity will precipitatethe bulk ofthe colloids in the sugarjuice which are very sensitive tolowering of the pH. The second dose of hydrogen zeolite introduced intoprecipitation chamber B causes a further lowering of the pH in saidchamber B to possibly 1.5 to 2.0. This second dose of hydrogen zeolitealso withdraws the balance of the metals from Ithe sugar juice. Ifsuiiicient acid is' not produced from the metal salts available in thesugar juice, it may be desirable to also add free acid through pipe 35to precipitation chamber B along with the carbona- 6 ceoizs zeolite inorder to lower the pH of the .juice to the desired extent. 'Ihe yacidused at this final stage in the precipitation .process may be phosphoricacid or any other desired acid. `The entire process takes place in thecold to prevent inversion of the sugar under the prevailing acidconditions, a maximum temperature of 50 C. or less being employed. Theacid conditions and rapid motion during the process serve to keep thebacteria and molds in the juice to a minimum until such time as thejuice is purified and sent to the evaporators where the heat completesthe sterilization of the juice. As indicated heretofore, the acidclarified juice from the second cell is preferably treated with an acidadsorption, or anion exchange, material to remove acidity prior toevaporation.

Alternate forms of the process are described as. follows:

Process 2 Using thetwo-cell compound precipitating apparatus or unit, wewould add phosphoric acid to the first cellin amounts sufficient toprecipitate the colloids. 'Ihe colloids are easily precipitated by aslight lowering of pH so that a large amount of phosphoric acid will notbe required.4 'I'he slimy colloidal mud from the first cell isdischargedby screw action. lThe efliuent from the iirst unit is passedinto the second unit and hydrogen carbonaceous zeolite is introducedinto the second unit tev remove metal ions from the sugar juice. As thiszeolite in the second cell is not plugged up with colloids from thejuice, it may be discharged from the second cell`by screw action andregenerated to be returned again tothe system. It will be understoodthat the acid contained in the clarified juice passing from the secondcell B can be removed by treating the juice with an anion exchange, oracid adsorption material as it is sometimes called, whereupon the juicecan be evaporated in theordinary manner.

Process 3 terial to adsorb all acids from the sugar juice anddeliver apure juice free of ash and acid suitable for evaporation down to apalatable syrup or Aliquid sugar. This acid absorbing material may becontinuously delivered from the third cell to be regenerated by the useof an alkali solution and returned for re-use in the third cell.

Process 4 Two cells are used and powdered hydrogen carbonaceous zeoliteis' introduced into the sugar juice in the first cell to precipitatecolloids, remove metal ions from the salts and to adsorb colored bodies.The purified juice from the first cell is passed to the second cell andacid adsorbing material is continuously introduced into the juice toremove all free acid from the juice and provide a juice which issuitable for evaporation to a .palatable syrup or liquid sugar. We wouldstate in conclusion that while the illustrated examples constitutepractical embodiments of our invention, we do not limit ourselvesprecisely to these details, since manifestly, the same may beconsiderably varied without departing from the spirit of the inventionas defined in the appended claims.

Having thus described our invention, we claim as new and desire tosecure by Letters Patent:

1. The process of producing puried sugar 7 juice, which comprises arapidly circulating body of previously formed precipitate with an amountof hydrogen zeolite sufficient to reduce the pH of the juice to between1.5 and 4.0-, withdrawing a portion of said precipitate from saidcirculating body, concentrating said precipitate, withdrawing a clariedportion of juice from said circulating body and treating said withdrawnjuiceV with an anion exchange material. x

2. The process of producing a purified sugar juice, which comprisesmixing the raw juice in a rapidly circulating body of partially spenthydrogen zeolite with an amount of fresh hydrogen zeolite suiicient toreduce the pH of the juice to between 1.5 and 4.0 so as to precipitatecolloids, remove metal ions and adsorb colored bod` mixing the raw juicein hydrogen zeolite suiiicient to reduce the pH of the juice to withinthel range of about 3.0 to 4.0 i

3. The process of purifying a. raw sugar juice, which comprises thesteps in sequence of rst mixing Ithe raw juice with a rapidlyIcirculating suspension comprising a body of juice undergoing treatmentcontaining precipitate accumulated from previously' treated juice and anamount of material :to produce a puriiied sugar juice capal 20 ble ofevaporation to a puriiied syrup.

I-IILDING B. GUSTAFSON. LEWIS A. PALEY.

